To form a unified composite of a polyimide-based resin molded product and acrylic rubber or fluororubber, there is a known method for vulcanization bonding of the resin molded product and the rubber using an adhesive. However, the method using an adhesive has complicated process and thus requires intricate process control, thereby causing high production costs. There is another problem that sufficient adhesion cannot always be obtained.
To address these problems, for example, Patent Document 1 proposes a method for bonding a resin to rubber, the method comprising treating the surface of the resin so that the average surface roughness is 0.1 or more, applying an adhesive to the treated surface, and vulcanization bonding of the rubber to the surface. However, this method requires, in addition to the process of using an adhesive, another process of treating the resin surface.